Odanacatib,effects of 16-month treatment and discontinuation of therapy on bone mass,turnover and strength in the ovariectomized rabbit model of osteopenia

Odanacatib (ODN) a selective and reversible cathepsin K inhibitor, inhibits bone resorption, increases bone mass and reduces fracture risk in women with osteoporosis. A 16-month (~ 7-remodeling cycles) study was carried out in treatment mode to assess the effects of ODN versus ALN on bone mass, remodeling status and biomechanical properties of lumbar vertebrae (LV) and femur in ovariectomized (OVX) rabbits. This study also evaluated the impact of discontinuing ODN on these parameters. Rabbits at 7.5 months post-OVX were dosed for 16-months with ODN (7.5 μM·h_0–24, in food) or ALN (0.2 mg/kg/wk, s.c.) and compared to vehicle-treated OVX- (OVX + Veh) or Sham-operated animals. After 8 months, treatment was discontinued in half of the ODN group. ODN treatment increased in vivo LV aBMD and trabecular (Tb) vBMD until reaching plateau at month 12 by 16% and 23% vs. baseline, respectively, comparable levels to that in Sham and significantly above OVX + Veh. LV BMD was also higher in ALN that plateaued around month 8 to levels below that in ODN or Sham. ODN treatment resulted in higher BMD, structure and improved biomechanical strength of LV and central femur (CF) to levels similar to Sham. ALN generally showed less robust efficacy compared to ODN. Neither ODN nor ALN influenced material properties at these bone sites following ODN or ALN treatment for 7 remodeling cycles in rabbits. ODN and ALN persistently reduced the bone resorption marker urinary helical peptide over study duration. While ALN reduced the bone formation marker BSAP, ODN treatment did not affect this marker. ODN also preserved histomorphometry-based bone formation indices in LV trabecular, CF endocortical and intracortical surfaces, at the levels of OVX + Veh. Discontinuation of ODN returned bone mass, structure and strength parameters to the comparable respective levels in OVX + Veh. Together, these data demonstrate efficacy and bone safety profile of ODN and suggests the potential long-term benefits of this agent over ALN with respect to accrued bone mass without long-term effects on bone formation.     

Treatment with eldecalcitol positively affects mineralization,microdamage, and collagen crosslinks in primate bone

Eldecalcitol (ELD), an active form of vitamin D analog approved for the treatment of osteoporosis in Japan, increases lumbar spine bone mineral density (BMD), suppresses bone turnover markers, and reduces fracture risk in patients with osteoporosis. We have previously reported that treatment with ELD for 6 months improved the mechanical properties of the lumbar spine in ovariectomized (OVX) cynomolgus monkeys. ELD treatment increased lumbar BMD, suppressed bone turnover markers, and reduced histomorphometric parameters of both bone formation and resorption in vertebral trabecular bone. In this study, we elucidated the effects of ELD on bone quality (namely, mineralization, microarchitecture, microdamage, and bone collagen crosslinks) in OVX cynomolgus monkeys in comparison with OVX-vehicle control monkeys. Density fractionation of bone powder prepared from lumbar vertebrae revealed that ELD treatment shifted the distribution profile of bone mineralization to a higher density, and backscattered electron microscopic imaging showed improved trabecular bone connectivity in the ELD-treated groups. Higher doses of ELD more significantly reduced the amount of microdamage compared to OVX-vehicle controls. The fractionated bone powder samples were divided according to their density, and analyzed for collagen crosslinks. Enzymatic crosslinks were higher in both the high-density (≥ 2.0 mg/mL) and low-density (< 2.0 mg/mL) fractions from the ELD-treated groups than in the corresponding fractions in the OVX-vehicle control groups. On the other hand, non-enzymatic crosslinks were lower in both the high- and low-density fractions. These observations indicated that ELD treatment stimulated the enzymatic reaction of collagen crosslinks and bone mineralization, but prevented non-enzymatic reaction of collagen crosslinks and accumulation of bone microdamage. Bone anti-resorptive agents such as bisphosphonates slow down bone remodeling so that bone mineralization, bone microdamage, and non-enzymatic collagen crosslinks all increase. Bone anabolic agents such as parathyroid hormone decrease bone mineralization and bone microdamage by stimulating bone remodeling. ELD did not fit into either category. Histological analysis indicated that the ELD treatment strongly suppressed bone resorption by reducing the number of osteoclasts, while also stimulating focal bone formation without prior bone resorption (bone minimodeling). These bidirectional activities of ELD may account for its unique effects on bone quality.     

Treatment with the combination of ibandronate plus eldecalcitol has a synergistic effect on inhibition of bone resorption without suppressing bone formation in ovariectomized rats

Bisphosphonates are widely used in the treatment of osteoporosis and contribute to the reduction of bone fractures. Ibandronate (IBN) is a highly potent, nitrogen-containing bisphosphonate, which is administered orally or intravenously at extended dosing intervals. Vitamin D or active vitamin D₃ derivatives are also used in the treatment of osteoporosis, and are often used in combination with other drugs. In this study, we investigated the effect of treatment with the combination of once-monthly s.c. dosing of IBN plus once-daily oral eldecalcitol (ELD), an active vitamin D₃ derivative, using aged ovariectomized (OVX) rats. Treatment was started the day after OVX, and analyses were performed 4, 8, and 12 weeks thereafter by determination of bone markers, bone mineral density, biomechanical properties, and histomorphometry. The combination treatment showed a synergistic effect in increasing both lumbar and femoral BMD, and resulted in a significant increase in bone ultimate load. The combination of IBN plus ELD acted synergistically to reduce bone resorption, whereas bone formation did not decrease any more than with monotherapy with either IBN or ELD. Bone formation independent of bone resorption (a process known as ‘minimodeling’) was not changed in vehicle treated OVX rats despite the increase in bone turnover. ELD upregulated minimodeling, which was however not diminished in the combination treatment. In conclusion, treatment with the combination of IBN plus ELD was beneficial in the treatment of osteoporosis in aged OVX rats. It exhibited a synergistic inhibitory effect on bone resorption and keeps bone formation at the level of sham controls. This uncoupling of bone resorption/bone formation was affected, to some extent, by minimodeling-based bone formation which is independent of bone resorption. This combination regimen which showed synergistic effect on BMD and bone ultimate load without inhibition of bone formation may be beneficial in long-term osteoporosis treatment to prevent bone fractures.     

Effect of odanacatib on bone turnover markers,bone density and geometry of the spine and hip of ovariectomized monkeys: A head-to-head comparison with alendronate

Odanacatib (ODN) is a selective and reversible Cathepsin K (CatK) inhibitor currently being developed as a once weekly treatment for osteoporosis. Here, effects of ODN compared to alendronate (ALN) on bone turnover, DXA-based areal bone mineral density (aBMD), QCT-based volumetric BMD (vBMD) and geometric parameters were studied in ovariectomized (OVX) rhesus monkeys. Treatment was initiated 10 days after ovariectomy and continued for 20 months. The study consisted of four groups: L-ODN (2 mg/kg, daily p.o.), H-ODN (8/4 mg/kg daily p.o.), ALN (15 μg/kg, twice weekly, s.c.), and VEH (vehicle, daily, p.o.). L-ODN and ALN doses were selected to approximate the clinical exposures of the ODN 50-mg and ALN 70-mg once-weekly, respectively. L-ODN and ALN effectively reduced bone resorption markers uNTx and sCTx compared to VEH. There was no additional efficacy with these markers achieved with H-ODN. Conversely, ODN displayed inversely dose-dependent reduction of bone formation markers, sP1NP and sBSAP, and L-ODN reduced formation to a lesser degree than ALN. At month 18 post-OVX, L-ODN showed robust increases in lumbar spine aBMD (11.4%, p < 0.001), spine trabecular vBMD (13.7%, p < 0.001), femoral neck (FN) integral (int) vBMD (9.0%, p < 0.001) and sub-trochanteric proximal femur (SubTrPF) int vBMD, (6.4%, p < 0.001) compared to baseline. L-ODN significantly increased FN cortical thickness (Ct.Th) and cortical bone mineral content (Ct.BMC) by 22.5% (p < 0.001) and 21.8% (p < 0.001), respectively, and SubTrPF Ct.Th and Ct.BMC by 10.9% (p < 0.001) and 11.3% (p < 0.001) respectively. Compared to ALN, L-ODN significantly increased FN Ct. BMC by 8.7% (p < 0.05), and SubTrPF Ct.Th by 7.6% (p < 0.05) and Ct.BMC by 6.2% (p < 0.05). H-ODN showed no additional efficacy compared to L-ODN in OVX-monkeys in prevention mode. Taken together, the results from this study have demonstrated that administration of ODN at levels which approximate clinical exposure in OVX-monkeys had comparable efficacy to ALN in DXA-based aBMD and QCT-based vBMD. However, FN cortical mineral content clearly demonstrated superior efficacy of ODN versus ALN in this model of estrogen-deficient non-human primates.     

Effects of combination treatment with alendronate and vitamin K2 on bone mineral density and strength in ovariectomized mice

Bisphosphonates increase bone mineral density (BMD) by suppressing remodeling space and elongating the duration of mineralization. Menatetrenone (vitamin K₂) reduces the incidence of fractures by improving bone quality through enhanced γ-carboxylation of bone glutamic acid residues of osteocalcin in osteoporotic patients. This study investigated the effects of combination treatment with alendronate (ALN) and vitamin K₂ on BMD and bone strength in ovariectomized (OVX) mice. Thirty-three female mice, 16 weeks of age, were assigned to four groups: (1) OVX-control group; (2) oral vitamin K₂ group; (3) subcutaneous ALN group; and (4) ALN + vitamin K₂ group. The treatment was started 4 weeks after OVX and continued for 4 weeks. BMD, geometric parameters measured by peripheral quantitative computed tomography, and mechanical strength at the femoral metaphysis and mid-diaphysis were evaluated after an 8-week treatment period. ALN alone significantly increased total BMD (20%, P < 0.05) and trabecular BMD (25%, P < 0.05), but not the mechanical parameters of the femur, compared with the OVX-control group. Combination treatment with ALN and vitamin K₂ increased not only total BMD (15%, P < 0.05) and trabecular BMD (32%, P < 0.05) but also maximum load (33%, P < 0.05) and breaking energy (25%, P < 0.05) of compression test at the distal metaphysis, and maximum load (20%, P < 0.05) and breaking force (33%, P < 0.05) of three-point bending test at the mid-diaphysis compared with the OVX-control group. These results suggest that ALN, alone or in combination with vitamin K₂, showed significant improvement in BMD, but that the combination treatment was more effective than ALN alone for improving bone strength in OVX mice.     

The resistance of cortical bone tissue to failure under cyclic loading is reduced with alendronate

Bisphosphonates are the most prescribed preventative treatment for osteoporosis. However, their long-term use has recently been associated with atypical fractures of cortical bone in patients who present with low-energy induced breaks of unclear pathophysiology. The effects of bisphosphonates on the mechanical properties of cortical bone have been exclusively studied under simple, monotonic, quasi-static loading. This study examined the cyclic fatigue properties of bisphosphonate-treated cortical bone at a level in which tissue damage initiates and is accumulated prior to frank fracture in low-energy situations. Physiologically relevant, dynamic, 4-point bending applied to beams (1.5 mm × 0.5 mm × 10 mm) machined from dog rib (n = 12/group) demonstrated mechanical failure and micro-architectural features that were dependent on drug dose (3 groups: 0, 0.2, 1.0 mg/kg/day; alendronate [ALN] for 3 years) with cortical bone tissue elastic modulus (initial cycles of loading) reduced by 21% (p < 0.001) and fatigue life (number of cycles to failure) reduced in a stress-life approach by greater than 3-fold with ALN1.0 (p < 0.05). While not affecting the number of osteons, ALN treatment reduced other features associated with bone remodeling, such as the size of osteons (− 14%; ALN1.0: 10.5 ± 1.8, VEH: 12.2 ± 1.6, × 10³ μm²; p < 0.01) and the density of osteocyte lacunae (− 20%; ALN1.0: 11.4 ± 3.3, VEH: 14.3 ± 3.6, × 10² #/mm²; p < 0.05). Furthermore, the osteocyte lacunar density was directly proportional to initial elastic modulus when the groups were pooled (R = 0.54, p < 0.01). These findings suggest that the structural components normally contributing to healthy cortical bone tissue are altered by high-dose ALN treatment and contribute to reduced mechanical properties under cyclic loading conditions.     

Effects of 16-month treatment with the cathepsin K inhibitor ONO-5334 on bone markers,mineral density,strength and histomorphometry in ovariectomized cynomolgus monkeys

We examined the effects of ONO-5334, a cathepsin K inhibitor, on bone markers, BMD, strength and histomorphometry in ovariectomized (OVX) cynomolgus monkeys. ONO-5334 (1.2, 6 and 30 mg/kg/day, p.o.), alendronate (0.05 mg/kg/2 weeks, i.v.), or vehicle was administered to OVX monkeys (all groups N = 20) for 16 months. A concurrent Sham group (N = 20) was also treated with vehicle for 16 months. OVX significantly increased bone resorption and formation markers and decreased BMD in lumbar vertebra, femoral neck, proximal tibia and distal radius. Alendronate suppressed these parameters to a level similar to that in the Sham-operated monkeys. ONO-5334 at doses 6 and 30 mg/kg decreased bone resorption markers to a level roughly half of that in the Sham group, while keeping bone formation markers level above that in the Sham monkeys. Changes in DXA BMD confirmed that ONO-5334 at doses 6 and 30 mg/kg increased BMD to a level greater than that in the Sham group in all examined sites. In the proximal tibia, in vivo pQCT analysis showed that ONO-5334 at doses 6 and 30 mg/kg suppressed trabecular BMD loss to the sham level. However, ONO-5334 increased cortical BMD, cortical area and cortical thickness to a level greater than that in the Sham group, suggesting that ONO-5334 improves both cortical BMD and cortical geometry. Histomorphometric analysis revealed that ONO-5334 suppressed bone formation rate (BFR) at osteonal site in the midshaft femur but did not influence OVX-induced increase in BFR at either the periosteal or endocortical surfaces. Unlike alendronate, ONO-5334 increased osteoclasts surface (Oc.S/BS) and serum tartrate-resistant acid phosphatise 5b (TRAP5b) activity, highlighting the difference in the mode of action between these two drugs. Our results suggest that ONO-5334 has therapeutic potential not only in vertebral bones, but also in non-vertebral bones.     

Minodronic acid ameliorates vertebral bone strength by increasing bone mineral density in 9-month treatment of ovariectomized cynomolgus monkeys

The effect of treatment for 9 months with minodronic acid, a nitrogen-containing bisphosphonate, on vertebral mechanical strength was examined in ovariectomized (OVX) cynomolgus monkeys. Forty skeletally mature female monkeys were randomized into four OVX groups and one sham group (n = 8) based on lumbar bone mineral density (BMD). OVX animals were treated orally with 15 and 150 μg/kg QD of minodronic acid or 500 μg/kg QD alendronate as a reference drug. Measurements of bone turnover markers and lumbar BMD were conducted at 0, 4 and 8 months. Measurements of bone mechanical strength and minodronic acid concentration in vertebral bodies were also performed. OVX resulted in a decrease in lumbar BMD and an increase in bone turnover markers at 4 and 8 months, compared to the sham group, and the ultimate load on the lumbar vertebra was decreased in OVX animals. Minodronic acid and alendronate prevented the OVX-induced increase in bone turnover markers and decrease in lumbar BMD. Minodronic acid at 150 μg/kg increased the ultimate load on lumbar vertebra compared to untreated OVX animals. Regression analysis revealed that the ultimate load was correlated with lumbar BMD and bone mineral content (BMC), and most strongly with the increase in lumbar BMD and BMC over 8 months. In a separate analysis within the sham-OVX controls and minodronic acid and alendronate treatment groups, the ultimate loads were also correlated with BMD and BMC. The load-BMD (BMC) correlation in the minodronic acid group showed a trend for a shift to a higher load from the basal relationship in the sham-OVX controls. These results indicate that treatment with minodronic acid for 9 months increases vertebral mechanical strength in OVX monkeys, mainly by increasing BMD and BMC.     

Effects of the combination treatment of raloxifene and alendronate on the biomechanical properties of vertebral bone

Raloxifene (RAL) and alendronate (ALN) improve the biomechanical properties of bone by different mechanisms. The goal here was to investigate the effects of combination treatment of RAL and ALN on the biomechanical properties of vertebral bone. Six‐month‐old Sprague‐Dawley rats (n = 80) were randomized into five experimental groups (sham, OVX, OVX + RAL, OVX + ALN, and OVX + RAL + ALN; n = 16/group). Following euthanization, structural and derived material biomechanical properties of vertebral bodies were assessed. Density and dynamic histomorphometric measurements were made on cancellous bone. The results demonstrate that the structural biomechanical properties of vertebral bone are improved with the combination treatment. Stiffness and ultimate load of the OVX + RAL and OVX + ALN groups were significantly lower than those of sham animals, but the combination treatment with RAL + ALN was not significantly different from sham. Furthermore, the OVX + RAL + ALN group was the only agent‐treated group in which the ultimate load was significantly higher than that in OVX animals (p < .05). Cancellous bone fractional volume (BV/TV_canc) and bone mineral density (aBMD) also were improved with the combination treatment. BV/TV_canc of the OVX + RAL + ALN group was 6.7% and 8.7% greater than that of the OVX + RAL (p < .05) and OVX + ALN (p < .05) groups, respectively. Areal BMD of the OVX + RAL or OVX + ALN groups was not significantly different from that in OVX animals, but the value in animals undergoing combination treatment was significantly higher than that in OVX or OVX + RAL animals alone and not significantly different from that in sham‐operated animals. Turnover rates of both the RAL + ALN and ALN alone groups were lower than in the RAL‐treated alone group (p < .05). We conclude that the combination treatment of raloxifene and alendronate has beneficial effects on bone volume, resulting in improvement in the structural properties of vertebral bone. © 2011 American Society for Bone and Mineral Research.     

Parathyroid hormone and bisphosphonate have opposite effects on stress fracture repair

This study was aimed to investigate the effects of Parathyroid hormone (PTH) and alendronate (ALN) on stress fracture repair. Stress fractures were induced in the ulnae of female adult rats. Animals were treated daily with vehicle, PTH (40 µg/kg) or alendronate (2 µg/kg), respectively. Bone mineral content (BMC) and bone mineral density (BMD) of bilateral ulnae were measured at two, four and eight weeks following induction of stress fracture. Histology at the ulna midshaft was undertaken at 2 and 4 weeks and mechanical testing was done at 8 weeks after stress fracture. PTH increased BMC significantly by 7% at 4 weeks and BMD and BMC significantly by 10% and 7% at 8 weeks compared to the control. Alendronate did not change BMD or BMC in comparison with the control. PTH significantly stimulated bone formation by 114% at 2 weeks, increased intracortical resorption area by 23% at 4 weeks, and enhanced the ultimate force of the affected ulnae by 15% at 8 weeks compared to the control. Alendronate significantly suppressed bone formation rate by 44% compared to the control at 4 weeks. These data indicate that PTH may accelerate intracortical bone remodeling induced by microdamage and alendronate may delay intracortical bone remodeling during stress fracture repair in rats. This study suggests that PTH may be used to facilitate stress fracture repair whereas bisphosphonates may delay tissue level repair of stress fractures.     

Adults with spastic cerebral palsy have lower bone mass than those with dyskinetic cerebral palsy

Adults with cerebral palsy (CP) are known to have low bone mass with an increased risk of fragility fracture. CP is classified into two major types: spastic (pyramidal) and dyskinetic (extrapyramidal). Spastic CP is the most common and is characterized by muscle hypertonicity and impaired neuromuscular control. By contrast, dyskinetic CP is characterized by mixed muscle tone with involuntary movements. The aim of this study was to elucidate the relationship between bone metabolism and subtype of CP. Fifty-eight adults with CP (aged 18 to 49 years, mean age 33.2 years; 32 men, 26 women) were included in this cross-sectional analysis. Lumbar spine and femoral bone mineral density (BMD) Z-scores were measured. Bone markers, including C-telopeptide of type I collagen (CTx) and osteocalcin (OCN), were also analyzed. Among these participants, 30 had spastic CP and 28 had dyskinetic CP. The Z-scores of lumbar spine BMD did not differ between the two types. However, the Z-scores of femur trochanteric BMD were significantly lower in participants with spastic CP than in those with dyskinetic CP (− 1.6 ± 1.2 vs. − 0.9 ± 1.1, p < 0.05). Seventy-four percent of participants with either type of CP had abnormally elevated CTx, while about 90% of participants showed normal OCN levels. When participants were subclassified into nonambulatory and ambulatory groups, the nonambulatory group had significantly lower BMD in the femur, including the trochanteric and total regions, whether they were spastic or dyskinetic (p < 0.05). Because the type of CP affects bone mass, nonambulatory spastic CP participants showed the lowest total hip region BMD among the four groups. These results reveal that reduced weight bearing and immobility related to CP cause a negative bone balance because of increased bone resorption, which leads to a lower bone mass. In addition, hypertonicity of the affected limbs in participants with spastic CP resulted in lower bone mass than in those with dyskinetic CP. Type of CP and degree of ambulatory function in adults with CP should be regarded as important factors affecting bone metabolism.     

Combination therapy with eldecalcitol and alendronate has therapeutic advantages over monotherapy by improving bone strength

Eldecalcitol (ED-71), a 2β-hydroxypropyloxy derivative of 1α,25(OH)(2)D(3), inhibits bone resorption more potently than does alfacalcidol while maintaining osteoblastic function in an estrogen-deficient, high-turnover osteoporosis rat model. Alendronate (ALN) has been reported to increase bone mass by suppressing bone resorption mainly by inducing apoptosis of osteoclasts. The aim of this study was to clarify the combination effect of ED-71 and ALN on bone loss in ovariectomized rats. Wistar-Imamichi rats (32weeks old) were ovariectomized and randomly assigned to 10 groups (n=9-11); 11 rats were sham-operated. Rats were orally administered either vehicle alone, ALN (0.05, 0.2mg/kg), ED-71 (0.015, 0.03μg/kg), or a combination of ALN and ED-71. The treatment started 2weeks after surgery and continued for 12weeks. ED-71 significantly increased calcium and phosphorus in serum and urine; however, the mean values were within the normal range. Bone mineral density (BMD) and maximum load in both the lumbar spine and femur significantly increased with ED-71 monotherapy, and showed a tendency to increase with ALN monotherapy. Compared with ALN monotherapy, the combination of ALN and ED-71 significantly increased BMD and maximum load in both the lumbar spine and femur, suggesting that the combination therapy is more beneficial than ALN monotherapy in this protocol. The combination treatment had an additive suppressive effect on eroded surface and osteoclast number, with the suppressive effect more potent than either ALN or ED-71 monotherapy. Moreover, the combination therapy partially counteracted the suppressive effects of ALN on bone formation and on the histomorphometric indices of osteoblast number and activity. Interestingly, ALN had no effect on the anabolic action of ED-71. In conclusion, the combination therapy of ALN and ED-71 has therapeutic advantages over ALN monotherapy in terms of improving bone mechanical strength without excessive suppression of bone turnover.     

Eating disorders,menstrual dysfunction,weight change and DMPA use predict bone density change in college-aged women

IntroductionThere are limited longitudinal studies that have evaluated bone mineral density (BMD) changes in college-aged women. Our objective was to simultaneously evaluate factors influencing 4-year BMD change.MethodsThis was a longitudinal cohort study of healthy, physically active women in the US Military Academy (n = 91; average age = 18.4 years). Assessments over four years included: height, weight, calcium intake, physical fitness, menstrual function (annual number cycles), oral contraceptives (OCs) or depot-medroxyprogesterone acetate (DMPA) use, and eating disorder behavior (Eating Disorder Inventory; (EDI)). BMD was measured annually at the lumbar spine and total hip by dual X-ray absorptiometry and calcaneal BMD by PIXI. Slope of 4 year BMD change at each skeletal site (spine total hip and calcaneus) was calculated for each woman.ResultsBMD gains occurred at the spine in 50% and the hip in 36% of women. In unadjusted analyses, spine bone gain was positively related to menstrual cycle frequency (p = 0.04). Spine and hip BMD loss occurred in those using DMPA (p < 0.01) and those with the highest EDI quartile scores (p < 0.05). BMD change was unrelated to OC use. Hip and calcaneus BMD decreased with weight loss (average 4.8 + 2.2 lb/year) as compared to those with stable weight/weight gain (p < 0.05). In multivariable analysis, spine BMD increase was significantly related to African American (AA) race, normal EDI score and normal menses. Hip BMD increase was related to AA race, weight increase and normal menses. DMPA use was associated with spine, hip, and calcaneus bone loss.ConclusionOn average, BMD may modestly increase in college-aged women, in the absence of risk factors. However, risk factors including subclinical eating disorders, weight loss, menstrual dysfunction and DMPA use can have significant detrimental effects on BMD in young healthy physically active women.     

Combination therapy with BMP-2 and a systemic RANKL inhibitor enhances bone healing in a mouse critical-sized femoral defect

Recombinant human BMP-2 (rhBMP-2) is a potent osteoinductive agent, but has been associated not only with bone formation, but also osteoclastogenesis and bone resorption. Osteoprotegerin (OPG) is a RANKL inhibitor that blocks differentiation and function of osteoclasts. We hypothesized that the combination of local BMP-2 (recombinant protein or a product of gene therapy) plus systemic OPG-Fc is more effective than BMP-2 alone in promoting bone repair. To test this hypothesis we used a mouse critical-sized femoral defect model. Col2.3eGFP (osteoblastic marker) male mice were treated with rhBMP-2 (group I), rhBMP-2 and systemic OPG (group II), rhBMP-2 and delayed administration of OPG (group III), mouse BM cells transduced with a lentiviral vector containing the BMP-2 gene (LV-BMP-2; group IV), LV-BMP-2 and systemic OPG (group V), a carrier alone (group VI) and administration of OPG alone (group VII). All bone defects treated with BMP-2 (alone or combined with OPG) healed, whereas minimal bone formation was noted in animals treated with the carrier alone or OPG alone. MicroCT analysis showed that bone volume (BV) in rhBMP-2 + OPG and LV-BMP-2 + OPG groups was significantly higher compared to rhBMP-2 alone (p < 0.01) and LV-BMP-2 alone (p < 0.001). Similar results were observed in histomorphometry, with rhBMP-2 alone defects exhibiting significantly lower bone area (B.Ar) compared to rhBMP-2 + OPG defects (p < 0.005) and LV-BMP-2 defects having a significantly lower B.Ar compared to all BMP-2 + OPG treated groups (p ≤ 0.01). TRAP staining demonstrated a major osteoclast response in the groups that did not receive OPG (rhBMP-2, LV-BMP-2 and sponge alone) beginning as early as 7 days post-operatively. In conclusion, we demonstrated that locally delivered BMP-2 (recombinant protein or gene therapy) in combination with systemically administered OPG improved bone healing compared to BMP-2 alone in a mouse critical-sized bone defect. These data indicate that osteoclasts can diminish healing responses to BMP-2 and that RANKL inhibition may thus accentuate BMP-2 efficacy.     

Duration-dependent effects of clinically relevant oral alendronate doses on cortical bone toughness in beagle dogs

Bisphosphonates (BPs) have been shown to significantly reduce bone toughness in vertebrae within one year when given at clinical doses to dogs. Although BPs also reduce toughness in the cortical bone when given at high doses, their effect on cortical bone material properties when given at clinical doses is less clear. In part, this may be due to the use of small sample sizes that were powered to demonstrate differences in bone mineral density rather than the bone's material properties. Our lab has conducted several studies in which dogs were treated with alendronate at a clinically relevant dose. The goal of this study was to examine these published and unpublished data collectively to determine whether there is a significant time-dependent effect of alendronate on toughness of the cortical bone. This analysis seemed particularly relevant given the recent occurrence of atypical femoral fractures in humans. Differences in the toughness of ribs taken from dogs derived from five separate experiments were measured. The dogs were orally administered saline (CON, 1 ml/kg/day) or alendronate (ALN) at a clinical dose (0.2 mg/kg/day). Treatment duration ranged from 3 months to 3 years. Groups were compared using ANOVA, and time trends analyzed with linear regression analysis. Linear regressions of the percent difference in toughness between CON and ALN at each time point revealed a significant reduction in toughness with longer exposure to ALN. The downward trend was primarily driven by a downward trend in post-yield toughness, whereas toughness in the pre-yield region was not changed relative to CON. These data suggest that a longer duration of treatment with clinical doses of ALN results in deterioration of cortical bone toughness in a time-dependent manner. As the duration of treatment is lengthened, the cortical bone exhibits increasingly brittle behavior. This may be important in assessing the role that long-term BP treatments play in the risk of atypical fractures of the femoral cortical bone in humans.     

Comparative effects of raloxifene and alendronate on fracture outcomes in postmenopausal women with low bone mass

The double-blind, randomized raloxifene alendronate comparison trial was the first study designed to compare two osteoporosis therapies head-to-head for fracture risk reduction. The original protocol planned to treat 3000 postmenopausal women with alendronate 10 mg/day (ALN) or raloxifene 60 mg/day (RLX) for 5 years, and to recruit women (50–80 years old) with a femoral neck bone mineral density (BMD) T-score between − 2.5 and − 4.0, inclusive, no prevalent vertebral fractures, and no prior bone-active agent use. The trial was stopped early, due to difficulty in finding treatment-naïve women to meet enrollment goals within the planned timeline, resulting in insufficient power to show non-inferiority between therapies in the primary endpoint (number of women with ≥ 1 new osteoporotic vertebral or nonvertebral fracture). Except for vertebral fractures, fracture analyses were based upon 1412 of the 1423 women randomized (mean age of 66 years). After 312 ± 254 days (mean ± SD), 22 women in the ALN group and 20 in the RLX group had new vertebral or nonvertebral fractures. Four women in the ALN group and none in the RLX group had moderate/severe vertebral fractures, a pre-specified endpoint (P = 0.04). Lumbar spine, femoral neck, and total hip BMD were increased from baseline at 2 years in each group (P < 0.001), with greater increases in the ALN group (each P < 0.05). Similar numbers of women in each group had ≥ 1 adverse event and discontinued due to an adverse event. The only adverse events with an incidence that differed between groups were colonoscopy, diarrhea, and nausea; each was more common with ALN treatment (each P < 0.05). One woman in each group had a venous thromboembolic event. One case of breast cancer occurred in each group. In summary, as this trial was terminated early, there was insufficient power to compare the fracture risks between alendronate and raloxifene. Safety profiles were as expected from clinical trial and post-marketing reports.Trial Registration: ClinicalTrials.gov Identifier NCT00035971.     

Associations among endocrine,inflammatory, and bone markers,body composition and weight loss induced bone loss

IntroductionWeight loss reduces co-morbidities of obesity, but decreases bone mass.PurposeOur aims were to 1) determine if adequate dairy intake attenuates weight loss-induced bone loss; 2) evaluate the associations of endocrine, inflammatory and bone markers, anthropometric and other parameters to bone mineral density and content (BMD, BMC) pre- and post-weight loss; and 3) model the contribution of these variables to post weight-loss BMD and BMC.MethodsOverweight/obese women (BMI: 28–37 kg/m²) were enrolled in an energy reduced (− 500 kcal/d; − 2092 kJ/d) diet with adequate dairy (AD: 3–4 servings/d; n = 25, 32.2 ± 8.8 years) or low dairy (LD: ≤ 1 serving/d; n = 26, 31.7 ± 8.4 years). BMD, BMC and body composition were measured by DXA. Bone markers (CTX, PYD, BAP, OC), endocrine (PTH, vitamin D, leptin, adiponectin, ghrelin, amylin, insulin, GLP-1, PAI-1, HOMA) and inflammatory markers (CRP, IL1-β, IL-6, IL-8, TNF-α, cortisol) were measured in serum or plasma. PA was assessed by accelerometry.ResultsFollowing weight loss, AD intake resulted in significantly greater (p = 0.004) lumbar spine BMD and serum osteocalcin (p = 0.004) concentration compared to LD. Pre- and post-body fat was negatively associated with hip and lumbar spine BMC (r = − 0.28, p = 0.04 to − 0.45, p = 0.001). Of note were the significant negative associations among bone markers and IL-1β, TNFα and CRP ranging from r = − 0.29 (p = 0.04) to r = − 0.34 (p = 0.01); magnitude of associations did not change with weight loss. Adiponectin was negatively related to change in osteocalcin. Factor analysis resulted in 8 pre- and post-weight loss factors. Pre-weight loss factors accounted for 13.7% of the total variance in pre-weight loss hip BMD; post-weight loss factors explained 19.6% of the total variance in post-weight loss hip BMD. None of the factors contributed to the variance in lumbar spine BMD.ConclusionAD during weight loss resulted in higher lumbar spine BMD and osteocalcin compared to LD. Significant negative associations were observed between bone and inflammatory markers suggesting that inflammation suppresses bone metabolism. Using factor analysis, 19.6% of total variance in post-weight loss hip BMD could be explained by endocrine, immune, and anthropometric variables, but not lumbar spine BMD.     

A comparative study of the bone metabolic response to dried plum supplementation and PTH treatment in adult,osteopenic ovariectomized rat

Dried plum has been reported to have potent effects on bone in osteopenic animal models, but the mechanisms through which bone metabolism is altered in vivo remain unclear. To address this issue, a study comparing the metabolic response of dried plum to the anabolic agent, parathyroid hormone (PTH), was undertaken. Six month-old female Sprague Dawley rats (n = 84) were sham-operated (SHAM) or ovariectomized (OVX) and maintained on a control diet for 6 wks until osteopenia was confirmed. Treatments were initiated consisting of a control diet (AIN-93M) supplemented with dried plum (0, 5, 15 or 25%; w/w) or a positive control group receiving PTH. At the end of 6 wks of treatment, whole body and femoral bone mineral density (BMD) were restored by the two higher doses of dried plum to the level of the SHAM group. Trabecular bone volume and cortical thickness were also improved with these two doses of dried plum. Dried plum suppressed the OVX-induced increase in bone turnover as indicated by systemic biomarkers of bone metabolism, N-terminal procollagen type 1 (P1NP) and deoxypyridinoline (DPD). Dynamic bone histomorphometric analysis of the tibial metaphysis revealed that dried plum restored the OVX-induced increase in cancellous bone formation rate (BFR) and mineralizing surface (MS/BS) to the SHAM group, but some doses of dried plum increased endocortical mineral apposition rate (MAR). As expected, PTH significantly increased endocortical MAR and BFR, periosteal BFR, and trabecular MAR and BFR beyond that of the OVX and maintained the accelerated rate of bone resorption associated with OVX. Dried plum up-regulated bone morphogenetic protein 4 (Bmp4) and insulin-like growth factor 1 (Igf1) while down-regulating nuclear factor T cell activator 1 (Nfatc1). These findings demonstrate that in the adult osteopenic OVX animal, the effects of dried plum differ from that of PTH in that dried plum primarily suppressed bone turnover with the exception of the indices of bone formation at the endocortical surface.     

A well-balanced diet combined or not with exercise induces fat mass loss without any decrease of bone mass despite bone micro-architecture alterations in obese rat

The association of a well-balanced diet with exercise is a key strategy to treat obesity. However, weight loss is linked to an accelerated bone loss. Furthermore, exercise is known to induce beneficial effects on bone. We investigated the impact of a well-balanced isoenergetic reducing diet (WBR) and exercise on bone tissue in obese rats. Sixty male rats had previously been fed with a high fat/high sucrose diet (HF/HS) for 4 months to induce obesity. Then, 4 regimens were initiated for 2 months: HF/HS diet plus exercise (treadmill: 50 min/day, 5 days/week), WBR diet plus exercise, HF/HS diet plus inactivity and WBR diet plus inactivity. Body composition and total BMD were assessed using DXA and visceral fat mass was weighed. Tibia densitometry was assessed by Piximus. Bone histomorphometry was performed on the proximal metaphysis of tibia and on L2 vertebrae (L2). Trabecular micro-architectural parameters were measured on tibia and L2 by 3D microtomography. Plasma concentration of osteocalcin and CTX were measured. Both WBR diet and exercise had decreased global weight, global fat and visceral fat mass (p < 0.05). The WBR diet alone failed to alter total and tibia bone mass and BMD. However, Tb.Th, bone volume density and degree of anisotropy of tibia were decreased by the WBR diet (p < 0.05). Moreover, the WBR diet had involved a significant lower MS/BS and BFR/BS in L2 (p < 0.05). Exercise had significantly improved BMD of the tibia possibly by inhibiting the bone resorption, as evidenced by no change in plasma osteocalcin levels, a decrease of CTX levels (p < 0.005) and trabecular osteoclast number (p < 0.05). In the present study a diet inducing weight and fat mass losses did not affected bone mass and BMD of obese rats despite alterations of their bone micro-architecture. The moderate intensity exercise performed had improved the tibia BMD of obese rats without any trabecular and cortical adaptation.     

Effects of combined elcatonin and alendronate treatment on the architecture and strength of bone in ovariectomized rats

We examined the combined effects of elcatonin (ECT) and alendronate (ALN) on bone mass, architecture, and strength in ovariectomized (OVX) rats. Fifty female Sprague Dawley rats, aged 13 weeks, were divided into Sham, OVX, OVX+ECT, OVX+ALN, and OVX+ECT+ALN groups (n = 10). Immediately after ovariectomy, ECT was administered at a dose of 15 units (U)/kg three times a week, and ALN was administered daily at a dose of 2.0 µg/kg, subcutaneously for 12 weeks. The three-dimensional architecture of the bone in the distal femoral metaphysis was analyzed using a microfocus X-ray computed tomography system (µCT), and bone strength was measured using a material-testing machine. Trabe-cular bone volume (BV/TV) and number (Tb.N) were significantly greater in the OVX+ECT and OVX+ALN groups than in the OVX group. In the OVX+ECT+ALN group, BV/TV and Tb.N were significantly greater when compared with those in the OVX+ECT and OVX+ALN groups. Trabecular thickness (Tb.Th) was significantly greater in the OVX+ECT+ALN group than in the OVX+ALN group. With regard to bone strength, the compression strength in the femoral metaphysis was significantly lower in the OVX group than in the Sham group. The reduction of compression strength was slightly lower in the OVX+ECT and OVX+ALN groups. In the OVX+ECT+ALN group, the compression strength in the femoral metaphysis significantly increased when compared with the OVX and OVX+ECT groups. These results suggest that the combined treatment of ECT and ALN does not alter the individual effects of each drug and that it exerts an additive effect on trabecular architecture and bone strength in OVX rats.